package com.stillalive.mq.mqserver.datacenter;

import com.stillalive.mq.common.MqException;
import com.stillalive.mq.mqserver.core.Binding;
import com.stillalive.mq.mqserver.core.Exchange;
import com.stillalive.mq.mqserver.core.MSGQueue;
import com.stillalive.mq.mqserver.core.Message;

import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 使用这个类来统一管理内存中的所有数据
 * 后续提供的一些方法可能会在多线程环境下被使用，因此要注意线程安全问题
 */
public class MemoryDataCenter {

    // key是exchangeName，value是exchange对象
    private ConcurrentHashMap<String, Exchange> exchangeMap = new ConcurrentHashMap<>();
    // key是queueName，value是MSGQueue对象
    private ConcurrentHashMap<String, MSGQueue> queueMap = new ConcurrentHashMap<>();
    // 第一个key是exchangeName，第二个key是queueName
    private ConcurrentHashMap<String, ConcurrentHashMap<String, Binding>> bindingsMap = new ConcurrentHashMap<>();
    // key是messageId，value是Message对象
    private ConcurrentHashMap<String, Message> messageMap = new ConcurrentHashMap<>();
    // key是queueName，value是一个Message链表
    private ConcurrentHashMap<String, LinkedList<Message>> queueMessageMap = new ConcurrentHashMap<>();
    // 未处理的消息
    // 第一个key是queueName，第二个key是messageId
    private ConcurrentHashMap<String, ConcurrentHashMap<String, Message>> queueMessageWaitAckMap = new ConcurrentHashMap<>();
    public void insertExchange(Exchange exchange) {
        exchangeMap.put(exchange.getName(), exchange);
        System.out.println("[MemoryDataCenter] 新交换机添加成功! exchangeName=" + exchange.getName());
    }

    public Exchange getExchange(String exchangeName) {
        return exchangeMap.get(exchangeName);
    }

    public void deleteExchange(String exchangeName) {
        exchangeMap.remove(exchangeName);
        System.out.println("[MemoryDataCenter] 交换机删除成功! exchangeName=" + exchangeName);
    }

    public void insertQueue(MSGQueue queue) {
        queueMap.put(queue.getName(), queue);
        System.out.println("[MemoryDataCenter] 新队列添加成功! queueName=" + queue.getName());
    }

    public MSGQueue getQueue(String queueName) {
        return queueMap.get(queueName);
    }

    public void deleteQueue(String queueName) {
        queueMap.remove(queueName);
        System.out.println("[MemoryDataCenter] 队列删除成功! queueName=" + queueName);
    }

    public void insertBinding(Binding binding) throws MqException {
        // 先查哈希表是否存在，不存在就创建一个
        // computeIfAbsent根据key查找value，如果value不存在就会执行表达式并创建value
        ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.computeIfAbsent(binding.getExchangeName(),
                k -> new ConcurrentHashMap<>());
        synchronized (bindingMap) {
            // 再根据 queueName 查一下. 如果已经存在, 就抛出异常. 不存在才能插入.
            if (bindingMap.get(binding.getQueueName()) != null) {
                throw new MqException("[MemoryDataCenter] 绑定已经存在! exchangeName=" + binding.getExchangeName() +
                        ", queueName=" + binding.getQueueName());
            }
            bindingMap.put(binding.getQueueName(), binding);
        }
        System.out.println("[MemoryDataCenter] 新绑定添加成功! exchangeName=" + binding.getExchangeName()
                + ", queueName=" + binding.getQueueName());
    }

    // 获取绑定，提供两个版本
    // 1. 根据exchangeName和queueName确定唯一一个Binding
    // 2. 根据exchangName获取到所有的Binding
    public Binding getBinding(String exchangeName, String queueName) {
        ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.get(exchangeName);
        if (bindingMap == null) {
            return null;
        }
        return bindingMap.get(queueName);
    }

    public ConcurrentHashMap<String, Binding> getBindings(String exchangeName) {
        return bindingsMap.get(exchangeName);
    }

    public void deleteBinding(Binding binding) throws MqException {
        ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.get(binding.getExchangeName());
        if(bindingMap == null){
            // 该交换机没有绑定任何队列. 报错.
            throw new MqException("[MemoryDataCenter] 绑定不存在! exchangeName=" + binding.getExchangeName()
                    + ", queueName=" + binding.getQueueName());
        }
        bindingMap.remove(binding.getQueueName());
        System.out.println("[MemoryDataCenter] 绑定删除成功! exchangeName=" + binding.getExchangeName()
                + ", queueName=" + binding.getQueueName());
    }
    // 添加消息
    public void addMessage(Message message)  {
        messageMap.put(message.getMessageId(), message);
        System.out.println("[MemoryDataCenter] 新消息添加成功！messageId=" + message.getMessageId());
    }

    // 根据 id 查询消息
    public Message getMessage(String messageId) {
        return messageMap.get(messageId);
    }

    // 根据 id 删除消息
    public void removeMessage(String messageId) {
        messageMap.remove(messageId);
        System.out.println("[MemoryDataCenter] 消息被移除! messageId=" + messageId);
    }

    // 发送消息到指定队列
    public void sendMessage(MSGQueue queue, Message message) {
        // 把消息放到对应的队列数据结构中
        // 根据队列的名字找到该队列的消息链表
        LinkedList<Message> messages = queueMessageMap.computeIfAbsent(queue.getName(), k -> new LinkedList<>());
        // 把数据加到messages里面
        synchronized (messages) {
            messages.add(message);
        }
        // 在这里把该消息插入到消息中心
        addMessage(message);
        System.out.println("[MemoryDataCenter] 消息被投递到队列中！messageId=" + message.getMessageId());
    }
    // 从队列中取消息
    public Message pollMessage(String queueName){
        // 根据队列名查找对应消息链表，如果没有消息说明队列中没有任何消息
        LinkedList<Message> messages = queueMessageMap.get(queueName);
        if(messages == null){
            return null;
        }
        synchronized (messages) {
            if(messages.size() == 0){
                return null;
            }
            // 链表中有元素，进行头删
            Message currentMessage = messages.remove(0);
            System.out.println("[MemoryDataCenter] 消息从队列中取出！messageId=" + currentMessage.getMessageId());
            return currentMessage;
        }
    }
    // 获取指定队列中消息的个数
    public int getMessageCount(String queueName){
        LinkedList<Message> messages = queueMessageMap.get(queueName);
        if(messages == null){
            return 0;
        }
        synchronized (messages) {
            return messages.size();
        }
    }

    // 添加未确认的消息
    public void addMessageWaitAck(String queueName, Message message) {
        ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.computeIfAbsent(queueName,
                k -> new ConcurrentHashMap<>());
        messageHashMap.put(message.getMessageId(), message);
        System.out.println("[MemoryDataCenter] 消息进入待确认队列! messageId=" + message.getMessageId());
    }

    // 删除未确认的消息(消息已经确认了)
    public void removeMessageWaitAck(String queueName, String messageId) {
        ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.get(queueName);
        if (messageHashMap == null) {
            return;
        }
        messageHashMap.remove(messageId);
        System.out.println("[MemoryDataCenter] 消息从待确认队列删除! messageId=" + messageId);
    }
    // 获取指定的未确认的消息
    public Message getMessageWaitAck(String queueName, String messageId) {
        ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.get(queueName);
        if (messageHashMap == null) {
            return null;
        }
        return messageHashMap.get(messageId);
    }

    // 数据从硬盘上恢复，硬盘上持久化存储的各个维度的数据都加载到内存中
    // 或者说把硬盘上的数据按照对应关系存在各个哈希表中
    public void recovery(DiskDataCenter diskDataCenter) throws IOException, MqException, ClassNotFoundException {
        // 清空之前的所有数据
        exchangeMap.clear();
        queueMap.clear();
        bindingsMap.clear();
        messageMap.clear();
        queueMessageMap.clear();
        // 恢复所有的交换机数据
        List<Exchange> exchanges = diskDataCenter.selectAllExchanges();
        for (Exchange exchange : exchanges) {
            exchangeMap.put(exchange.getName(), exchange);
        }
        // 恢复所有的队列数据
        List<MSGQueue> queues = diskDataCenter.selectAllQueues();
        for(MSGQueue queue : queues){
            queueMap.put(queue.getName(), queue);
        }
        // 恢复所有的绑定数据
        List<Binding> bindings = diskDataCenter.selectAllBindings();
        for(Binding binding : bindings){
            ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.computeIfAbsent(binding.getExchangeName(),
                    k -> new ConcurrentHashMap<>());
            bindingMap.put(binding.getQueueName(), binding);
        }
        // 恢复所有的消息数据
        // 遍历所有的队列，根据每个队列的名字获取到所有的消息
        for(MSGQueue queue : queues){
            LinkedList<Message> messages = diskDataCenter.loadAllMessageFromQueue(queue.getName());
            queueMessageMap.put(queue.getName(), messages);
            for(Message message : messages){
                messageMap.put(message.getMessageId(), message);
            }
        }
        // 未确认的消息，在等待ACK的过程中会被恢复为“未被取走的消息”，重新加载硬盘数据时会统一加载进来
    }
}
